This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The goal of this project is to obtain a detailed sampling of the equilibrium fluctuations of the D. melanogaster engrailed homeodomain by performing a 140 microsecond simulation in explicit solvent. This 54 residue, 3-helix protein has an experimental unfolding rate of 2.1E+03/sec, suggesting that a millisecond-scale simulation will likely exhibit significant fluctuations, possibly including partial or full unfolding and refolding. The data produced from the Anton simulation will be serve two broad aims: (a) to characterize the protein's equilibrium fluctuations over long timescales, and (b) to carefully test and validate a number of computational methods that the Co-PIs have (independently) developed.